Effective collection, management, and control of information have become a central component of modern business processes. To this end, many businesses, both large and small, now implement computer-based information management systems.
Data management is an important component of computer-based information management systems. Many users implement storage networks to manage data operations in computer-based information management systems. Storage networks have evolved in computing power and complexity to provide highly reliable, managed storage solutions that may be distributed across a wide geographic area.
Data redundancy is one aspect of reliability in storage networks. A single copy of data is vulnerable if the network element on which the data resides fails. If the vulnerable data or the network element on which it resides can be recovered, then the loss may be temporary. However, if either the data or the network element cannot be recovered then the vulnerable data may be lost permanently.
Storage networks implement remote copy procedures to provide data redundancy and failover procedures to provide data consistency in the event of a failure of one or more network elements. Remote copy procedures replicate one or more data sets resident on a first storage site onto at least a second storage site. A data consistency group (DCG) is a data set comprising a plurality of storage units, each containing a portion of an aggregated data set, with each storage unit having the potential to be individually replicated. The storage units may be logical or physical. A DCG implemented at the disk array level enables data sets to be aggregated across multiple logical units with the assurance that any unsuccessful replication will immediately halt all local and remote write operations, such that the aggregated primary data set and the aggregated secondary data set remain consistent, and therefore useful for continuing operations.
Large storage networks may comprise dozens, or even hundreds of storage cells, and may have hundreds, or even thousands of host computers that execute write operations to data sets in the storage network. Effective storage management techniques must ensure data consistency in DCGs implemented in complex storage networks.